Judgment lock for occupant detection air bag control

ABSTRACT

Systems and methods for controlling the sensing of an occupant in a seating area are provided. The occupant is characterized as one of an adult, child or other category. One characterization change parameter, such as a hysteresis time period or thresholds for characterization, is applied for a first time period. After that time period, the characterization change parameter is changed. For example, if the characterization stays the same for ten seconds, the hysteresis is changed from five to ten seconds. As another example, if the characterization stays the same for one minute, the thresholds associated with that characterization are broadened to decrease the likelihood of a change in characterization. In some systems and methods, a confidence parameter or probability associated with the characterization is used to control the changes of the characterization change parameter. In some systems and methods, the characterization change parameter is reset in response to one of (a) a no occupant characterization or (b) characterizing the occupant as a different one of the at least two categories consecutively for a current hysteresis time period.

BACKGROUND

[0001] The present invention is related to passenger detection systems,and in particular to passenger detection systems that classify anattribute of a passenger of an automobile in which an air bag device isinstalled.

[0002] Air bag devices ease the shock that a passenger experiencesduring an automobile collision. Air bags may be installed in front ofthe driver's and passenger's seats. Air bags may be installed in otherlocations, such as to the side of a passenger.

[0003] Many air bags are designed to deploy in front of the torso of anadult passenger seated in the seat. When a rear facing infant seat(hereafter RFIS) is located on the front passenger seat, it is desirablefor the passenger-side air bag not to deploy. It may also be desirablefor the air bag not to deploy for a forward facing child seat (hereafter“FFCS”), child or small adult. Likewise, deployment may be limited forside impact airbags based on whether a child or short person is leaningtowards the air bag. Other reasons for preventing or limiting deployment(e.g. deploying with less force) may exist.

[0004] Passenger detection sensors have been proposed for detecting aRFIS, an FFCS or children. Systems using electric fields to detectcharacteristics of a load in a seat are disclosed in U.S. Pat. Nos.5,948,031, 6,329,913, 6,329,914, (Ser. No. 09/798,788, filed Mar. 2,2001) and ______ (Ser. No. 10/033,585, filed Nov. 2, 2001). Othersystems using capacitive sensing, such as systems to detect a change inphase or frequency due to the presence of a passenger, have also beenproposed. Both types of systems rely on transmission and/or receptionfrom one or more antennas or electrodes. Other passenger detectionsystems use ultrasound, infrared, light electromagnetic energy or othertransmissions or receptions to detect one or more characteristics ofoccupants. Yet another type of detection system uses weight sensors,strain gauges, pattern recognition or other techniques or devices.

[0005] These occupant detection sensors are subjected to changingenvironmental conditions. Acceleration, deceleration, shocks from bumpsor potholes or other factors may cause the sensor measurements orjudgments to change frequently. The change is caused by a direct effecton the sensor or the shifting of an occupant's position in response tothe changing conditions. As a result, the judgment and any indicatorsblink or change even though the detected occupant is the same. Thesensor judgment may change even more frequently or in response to lesserchanges in the environment for occupants close to judgment thresholds,such as a child just large enough to be classified as an adult or anadult small enough to be near the child threshold. Drivers may assumethe changing judgment is associated with a faulty system and attempt toget the system fixed when nothing is wrong.

[0006] To avoid frequent changes in occupant detection based on changingenvironmental conditions, a five second hysteresis has been used. Thefinal judgment or measurement conclusion changes only if five continuousseconds of measurements indicate the different judgment. However, someoccupant movements or environmental conditions, such as extended turnson highway ramps or acceleration up a long hill, can continue for morethan 5 seconds.

SUMMARY

[0007] The present invention is defined by the following claims, andnothing in this section should be taken as a limitation on those claims.By way of introduction, the preferred embodiments described belowinclude systems and methods for controlling the sensing of an occupantin a seating area. The occupant is characterized as one of an adult,child or other category. One characterization change parameter, such asa hysteresis time period or thresholds for characterization, is appliedfor a first time period. After that time period, the characterizationchange parameter is changed. For example, if the characterization staysthe same for ten seconds, the hysteresis is changed from five to tenseconds. As another example, if the characterization stays the same forone minute, the thresholds associated with that characterization arebroadened to decrease the likelihood of a change in characterization.

[0008] In some systems and methods, a confidence parameter orprobability associated with the characterization is used to control thechanges of the characterization change parameter. In some systems andmethods, the characterization change parameter is reset in response toone of (a) a no occupant characterization or (b) characterizing theoccupant as a different one of the at least two categories consecutivelyfor a current hysteresis time period.

[0009] Further aspects and advantages are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a block diagram of one embodiment of a vehicle passengerdetection system for controlling the sensing of an occupant in a seatingarea.

[0011]FIG. 2 is a flow chart diagram of one embodiment of controllingthe sensing of an occupant.

DETAILED DESCRIPTION OF THE INVENTION

[0012] To avoid frequently changing characterizations of an occupant,the characterization is made progressively more difficult to change. Thedifficulty is increased by a greater hysteresis time period and/orchanging the thresholds or algorithm used to characterize the occupantto be more inclusive for a current characterization. A confidence of thecurrent characterization may be used to determine the level or amount ofdifficulty to change. The increased difficulty is decreased either bydetecting an unoccupied seat or by consistent determination of adifferent characterization using the greater hysteresis or moreinclusive thresholds.

[0013]FIG. 1 shows a vehicle passenger detection system 10 of oneembodiment for controlling the sensing of an occupant in a seating area.The system 10 includes one or more sensors 12, a control processor 14,an air bag controller 16 and an air bag 18. Additional, different orfewer components may be used, such as combining the control processor 14and air bag controller 16. The vehicle passenger detection system isused to characterize or detect a passenger in an automobile or othervehicle. In one embodiment described below, the vehicle passengerdetection system is used for controlling, limiting or alteringdeployment of air bags. The vehicle passenger detection system can beused for other purposes, such as controlling settings or operation ofany vehicle system based on an occupant characteristic.

[0014] The system 10 may be implemented with various circuits and/ormethods.

[0015] Some exemplary electric field based circuits and methods arediscussed in U.S. Pat. Nos. 5,948,031, 6,161,070, 6,329,913, 6,329,914,______ (Ser. No. 09/798,788, filed Mar. 2, 2001) and ______ (Ser. No.10/033,585, filed Nov. 2, 2001), the disclosures of which areincorporated herein by reference. In alternative embodiments, thevehicle passenger detection system 10 comprises weight, capacitive,ultrasound, infrared, visible light or other sensing systems fordetecting the presence of a passenger. Any device now known or laterdeveloped for detecting an occupant may be used.

[0016] The sensor 12 comprises a passive or active sensor fortransmitting or receiving energy as part of an occupant detectionsystem. In one embodiment, the sensor 12 comprises at least oneelectrode antenna. In another embodiment, the occupant detection sensor12 comprises a plurality of electrodes. The electrodes are of any shapeand position. For example, rectangular strips of electrodes arepositioned in two or more layers separated by air or a divider (e.g.foam insulator).

[0017] Electrodes include a single wire, single conducting layer, two ormore conductors, capacitance sensors, antenna or other structure fortransmitting or receiving electromagnetic energy. In alternativeembodiments, the sensor 12 comprises a weight sensor, strain gauge,piezoelectric material, micro-machined component, ultrasound transducer,diode, light sensor, camera, semiconductor or other device forgenerating or detecting energy, such as ultrasound, infrared, light orother energy.

[0018] The sensor 12 is positioned adjacent to a seating area 20. Forexample, the sensor 12 is in a seat 22. As another example, the sensor12 is in a steering column or dashboard in front of the seat 22, in theroof above the seat 22, on a door beside the seat 22 or on a floor belowthe seat 22. Other positions may be provided. Multiple sensors of a sameor different type may be positioned in the same or different locations.The same or different sensors may be used for detecting one occupant ormultiple occupants in different seating areas.

[0019] In one embodiment using either or both of capacitive or electricfield sensing, minute electric fields between two electrodes positionedin the passenger seat are detected. An electric field is created as aresult of the potential difference between the electrodes when ahigh-frequency, low-voltage signal is applied to one electrode and theother electrode is connected to ground. This electric field produces acurrent (the receive current) flowing from one electrode(non-transmitting) to ground. If a body (passenger or occupant) ispresent in the electric field, disturbances in the electric field alterthe current. Likewise, a current (the loading current) provided to thetransmitting electrode is also altered in response to the presence ofthe body. A loading current may be used without a receive current ormeasurement in another electrode.

[0020] The body acts as a capacitor having one terminal connected toground. The impedance (resistance and capacitance) of the body shuntsthe electric field to ground. When the body is in the vehicle seat,changes in the current flowing at the transmitting and any receivingelectrodes occur in response to the electrical characteristics of thebody. For example, the loading current is larger for closer and/orlarger bodies. As another example, the frequency response, phase orother signal characteristic changes in response to the occupant. Usingthese phenomenon, the presence of a passenger in the seat 22 is detectedby comparing the detected current with a known value. In particular, oneor more characteristics of the object in the seat are obtained,including whether or not the object is an adult-sized person sittingnormally in the seat. By using electrodes at known or predictabledifferent distances from the object, even more information is obtained.Therefore, the presence, location and other characteristics of theoccupant in the seat 22 is precisely detected.

[0021] The control processor 14 electrically connects with the occupantdetection sensor 12 of one or more seating areas for detecting acharacteristic of one or more occupants. The control processor 14comprises one or more of an application specific integrated circuit,processor, digital signal processor, analog components, digital deviceor combination thereof. For example, a microprocessor manufactured byNEC Corporation of Japan is used and includes analog to digitalconverters. In one embodiment, the control processor 14 includes thedrivers and circuits for measuring signals to or from the occupantdetection sensor 12. The occupant detection sensor 12 comprises just thepassive antenna or the antenna and some associated circuitry. Thecontrol processor 14 is positioned in the vehicle seat 22 or elsewherein the vehicle.

[0022] The control processor 14 characterizes the occupant in theseating area as one of at least two categories, such as adult, smalladult, child, rear-facing child seat, forward facing child seat or othercategory. The categories may also include position information, such asa child leaning towards a door, a standing child or a properly seatedchild. Using one or more judgments, a final characterization is output.

[0023] The control processor 14 applies a characterization changeparameter for a first time period and alters the characterization changeparameter after the first time period. For example, the controlprocessor 14 initially allows a change of characterization aftermeasurements or judgments indicate the different characterization forfive seconds, other time period or number of judgments. Thischaracterization change parameter is a hysteresis parameter or timeperiod. The characterization change is based on another characterizationchange parameter, the thresholds applied to categorize the occupant.Other characterization change parameters may be used. Any parameter forcharacterizing the occupant may be altered as a characterization changeparameter, limiting any change of characterization differently.

[0024] After a certain amount of time, an event, a measurement, aprobability or other designation, one or more characterization changeparameters are altered, such as increasing the hysteresis time period ornumber of consecutive judgments before allowing a change ofcharacterization. As another example, a characterization threshold, suchas one or more of size, weight, surface area or other judgmentindicator, is altered so the current characterization category is moreinclusive. These alterations make the current characterizations morelikely to continue, avoiding frequent changes in the characterization.Each judgment is more likely to match the current characterization beingoutput. Other triggers may be used to further adjust a same or differentcharacterization change parameter at other times.

[0025] The control processor 14 is also operable to determine aconfidence parameter indicating a probability that the currentcharacterization is correct. For example, the probability or confidenceis calculated as a ratio of occurrences of the current judgment to atotal number of judgments in a time period. The amount of time beforealteration may be based on the confidence parameter. For example, thethresholds of a characterization are adjusted earlier to be moreinclusive where the probability of a correct characterization are high.Where the probability is low, the thresholds are only adjusted after alonger time period of judgments consistent in characterization. Inalternative embodiments, the confidence parameter is not calculated.

[0026] The control processor 14 is also operable to reset thecharacterization change parameter. For example, the hysteresis orthresholds are reset to starting levels (e.g. a 10 second hysteresisreset to a 5 second hysteresis) where an empty seat is detected. If theoccupant leaves the seat, a different occupant may then enter the seat,so the characterization change parameters are reset or unlocked. Asanother example, the hysteresis or thresholds are reset to startinglevels where the occupant is continually judged as in a differentcategory despite the altered characterization change parameters. If theoccupant is consistently detected as a child after increasing thehysteresis time period and/or altering thresholds based on a previouscharacterization of the occupant as an adult, the characterizationchange parameters are unlocked or returned to starting levels. Otherreset triggers may be used.

[0027] The air bag controller 16 connects with the control processor 14.The air bag controller 16 responds to crash sensors and the controlprocessor 14 to trigger deployment of the air bag 18. When a crash issensed, but the control processor 14 indicates a child or otherrestricted class occupant, the air bag controller 16 may not deploy theair bag 18. When a crash is sensed and the control processor 14indicates an adult or properly positioned occupant, the air bagcontroller 16 may cause the air bag 18 to deploy. The air bag controller16 may also control the force, speed or other characteristic ofdeployment in response to an indication of the category of occupant fromthe control processor 14. In other embodiments, the control processor 14and sensor 12 are used to detect a crash, such as detecting based onsudden head movement, and cause deployment of the air bag 18.

[0028] In one embodiment, a LED, liquid crystal display or other outputdevice is provided to indicate the status of the characterization. Forexample, the LED is illuminated when the air-bag is disabled due tocharacterization as an child, small adult, child seat or other category.By locking the characterization or altering the characterization changeparameter, this output is less likely to change or blink.

[0029]FIG. 2 shows a vehicle passenger detection flow chart of oneembodiment for controlling sensing of an occupant in a seating area. InFIG. 2, the term “state prediction” is the output decision orcharacterization of the system after averaging, hysteresis or otheroperations based on one or more judgments. The term “immediate” is asystem judgment for one discrete measurement cycle, including anyaveraging with previous cycles to output the current judgment.

[0030] In general, an occupant in a seating area is characterized, suchas categorizing as a child or adult. Judgments for the characterizationcontinually repeat, such as three or other number a minute. Initially,any changes in the characterization is limited by hysteresis. The new ordifferent judgment of the characterization occurs over five seconds or anumber of times before a new characterization is implemented orrecognized. If the judgments of characterization are consistent for afirst time period or number of characterizations, such as 10 seconds or30 characterizations, a soft lock is implemented. A characterizationchange parameter is altered, such as increasing the hysteresis timeperiod to 10 seconds or 30 characterizations. If after a minute or othertime period, the judgments of characterization are still consistent, ahard lock is implemented for high probability characterizations. Wherethe confidence in the characterization is high, one, more or all of thethresholds associated with the current characterizations are broadened,such as increased or decreased, so more measurements are likely to bejudged as the current characterization. If the judgments ofcharacterization are still consistent after another minute or other timeperiod, a hard lock is implemented for the characterization regardlessof probability. If the characterization changes even with the currentcharacterization change parameter settings, the characterization changeparameters are reset and the process begins again.

[0031] In act 30, the ignition of the vehicle is turned on. Otherbeginning triggers may be used. In act 32, an initial state predictionor judgment is made. This initial judgment is used as the outputcharacterization. If the seating area is empty, the judgments ofcharacterization continue with a hysteresis of five seconds in act 34.Any of various information may indicate an empty seating area, such ascomparing the actual current or phase readings of the sensor 12 to athreshold (e.g. current readings within a threshold amount of acalibrated empty reading), calculating a value for comparison to athreshold (e.g. total capacitance calculated and compared to athreshold) or combinations thereof. The characterization remains asempty until judgments of a non-empty characterization are repeated forfive seconds or for 15 occurrences. Other hysteresis time or number ofjudgment values may be used.

[0032] After a change of characterization from empty or an initialdetermination of an occupant, the occupant is characterized as one of atleast two categories in act 36. For example, the occupant is categorizedas a child or an adult. In other embodiments, the occupant iscategorized as (1) an adult in one or more positions, (2) a child orsmall adult in one or more positions, (3) a child in a forward facingchild seat, (4) an infant in an rear facing child seat, or (5) anotherobject. Additional or different categorizations may be used. Thecharacterization is preferably determined by comparison to expectedmeasurements. Alternatively, an algorithm that determines thedistribution of the load is used to classify the occupant as largeenough for air bag activation or to small for air bag activation. In yetanother alternative embodiment, a function of the measurementsdetermines the classification.

[0033] In one embodiment, the system 10 performs the following functionsin a serial manner to judge or characterize the occupant: 1) outputreadings are compensated for cable length, 2) calculations are performedto correct for grounded occupant condition, 3) the complex impedance ofthe load is calculated using frequency data associated with differentfrequencies, 4) a distance between layers of electrodes is calculated,5) the effective surface area of the occupant is calculated, 6) thedistance of the occupant over a top-layer of electrodes is calculated,7) judgment parameters to be used for occupant categorization arecalculated, and 8) the judgment parameters are used to characterize theoccupant based on initial predetermined thresholds. In one embodiment,the judgment parameters include weight, average of effective surfaceareas, maximum of effective surface areas, relative mass, the weightmultiplied by the relative mass (i.e. mass product), total capacitanceof load, and/or other values. If all of these parameters are abovethresholds, the occupant is judged as an adult. If one judgmentparameter is below the associated threshold, the occupant is judged as achild. In alternative embodiments, different thresholds are used, and/ortwo or more judgment parameters are needed to categorize the occupant asa child.

[0034] Once the occupant is characterized, the characterization islocked for a time period, such as 5 second hysteresis time period. Asthe processes for judgments of characterizing the occupant aresequentially repeated, subsequent different judgments are discarded oraveraged and ignored until after the hysteresis period of time. Thecharacterization provided as a control signal is not allowed to changeuntil after the hysteresis time period. The characterization is notchanged unless a certain number of consecutive or substantiallyconsecutive judgments indicate that the characteristic has changed. Inan alternative embodiment, the characterization changes without a timeor number of instances limitation.

[0035] In act 38, a counter is started. For example, a timer is startedor the number of judgments are counted. In act 40, the counter counts to10 seconds, other time period or number of judgments as a first timeperiod. The initial hysteresis, characterization thresholds and othercharacterization change parameters are applied during this time period.If the characterization changes with these current or initialcharacterization change parameters, the process returns to one of acts34 or 36. For example, if a windowed average or all of the judgmentsindicate a characterization of child instead of an initial adult forfive consecutive seconds based on comparison to current characterizationthresholds, the characterization is changed to child.

[0036] If the characterization does not change during this first timeperiod, the hysteresis, characterization thresholds or othercharacterization change parameter are increased in acts 42 and 44. Inboth of acts 42 and 44 of the embodiment of FIG. 2, the hysteresis timeperiod is increased from five seconds to ten seconds or from 15judgments to 30 judgments. Alternatively, if a certain number ofjudgments of characterizations during the time period do not indicate achange, one or more characterization change parameters are altered. Theratio of adult judgments to the total number of judgments (e.g. 30)during the first time period is determined. If the ratio is greater thanor equal to 0.6, the category is set or remains as adult in act 42. Ifthe ratio is less than or equal to 0.4, the category is set or remainsas child in act 42. In act 44, if the ratio is greater than 0.4 and lessthan 0.6, the output characterization is not changed. For ratios thatfall outside of these or other limits, the characterization is changedand the process reverts to acts 34 or 36. Alternatively, the ratio isnot used and the characterization parameter is changed without responseto the confidence in the current characterization.

[0037] In act 46, the counter continues to increment. During thisadditional time period, the current hysteresis (e.g. the altered 10second hysteresis), characterization thresholds and othercharacterization change parameters are applied. If the characterizationchanges even with these current characterization change parameters, theprocess returns to one of acts 34 or 36 and the characterization changeparameters are reset. In act 48, the counter counts to one minute, othertime period or number of judgments (e.g. 180 judgments).

[0038] If the characterization does not change during this additionaltime period, a hysteresis, characterization thresholds or othercharacterization change parameter is altered in acts 50 or kept the samein act 52. In act 50, changes in the output characterization are furtherlimited. The same or a different characterization change parameter thanthe characterization change parameter altered in acts 42 or 44 isaltered after the additional time period. In the embodiment of FIG. 2,one, more or all of the characterization thresholds are changed by 20%or other amount. The thresholds are changed to more broadly define thecurrent characterization, such as increasing the threshold values somore measurements likely indicate a child or decreasing the thresholdvalues so more measurements likely indicate an adult. For example, theweight, relative mass, average surface area, maximum surface area andmass product thresholds are decreased so that future judgments morelikely indicate an adult characterization. Different thresholds may bechanged by different amounts and increased or decreased. Alternativelyor additionally, the previously altered hysteresis or othercharacterization change parameter is further altered.

[0039] A confidence parameter is calculated to select between the hardlock or alteration of act 50 or the continued operation without furtherchange of the characterization change parameters of act 52. Theconfidence parameter indicates the probability that the occupant iscorrectly categorized. For example, the ratio of adult judgments to thetotal number of judgments during the first (e.g. 10 seconds or 30judgments), additional, or first plus additional time period isdetermined. In one embodiment, the judgments used include all or mostvalid judgments (e.g. 180 judgments) acquired since initializing thecounter in act 38. The ratio calculated for acts 50 and 52 samples overa longer time period than the ratio of acts 42 and 44. Other ratios orindicators of confidence or probability may be used. If the ratio isgreater than or equal to 0.6, the characterization is set or remains asadult in act 50. If the ratio is less than or equal to 0.4, thecharacterization is set or remains as child in act 50.

[0040] If the ratio is between 0.4 and 0.6, a lesser confidence orprobability of correct characterization is indicated. Thecharacterization is more borderline. In act 52, the outputcharacterization or category and the characterization change parametersare not altered, but the current characterization is maintained.Alternatively, the characterization change parameters are reset, alteredto further lock the current characterization but not as much as for act50, or altered to reduces the soft lock of acts 42 and 44 withoutresetting the characterization change parameters. By maintaining thesame characterization change parameters in act 50, the time period forapplication of the current characterization change parameters (e.g.altered once in acts 42 and 44) is increased. This time period is afunction of the confidence parameter.

[0041] In act 54, the counter continues to increment where thecharacterization change parameters were not further changed or hardlocked in act 50. During this additional time period, the currenthysteresis (e.g. the altered 10 second hysteresis), characterizationthresholds and other characterization change parameters are applied. Ifthe characterization changes even with these current characterizationchange parameters, the process returns to one of acts 34 or 36 and thecharacterization change parameters are reset. In act 56, the countercounts to two minutes, other time period or number of judgments.

[0042] In act 58, the characterization change parameters are altered asa function of the confidence in the current characterization. The amountof confidence is reduced as compared to acts 50 and 52. For example, ifthe ratio is less than 0.5, the characterization is set to or remains asa child. If the ratio is more than 0.5, the characterization is set toor remains as an adult. If the ratio is equal to 0.5, the currentcharacterization is used. Regardless of the characterization, thecharacterization thresholds are altered by 20% or other amount. For achild characterization, the thresholds are increased by 20%. For anadult characterization, the thresholds are decreased by 20%. Otheramounts of alteration or characterization change parameters to bealtered may be used.

[0043] Other processes than shown in FIG. 2 may be used. For example,three or more alternative alterations (e.g. acts 42 verses 44 or acts 50verse 52) of characterization change parameters may be used as afunction of different levels of confidence. Any number of alterations,such as just one, two, three or more, may be used. Any of time, numberof judgments, confidence, probability or other information may be usedfor triggering alteration. The confidence value may be calculated as afunction of a moving window of a previous number of judgments, for allthe judgments made since initiating the counter in act 38, or othernumber of judgments. The confidence value may be based on otherstatistical calculations including or not including the number ofjudgments. The ratio of child judgments to total judgments may be usedinstead of the ratio of adult judgments to total judgments.

[0044] The characterization change parameter(s) are reset to initiallevels in response to one of: (a) a no occupant judgment or (b) judgingthe occupant as a different one of the at least two categoriesconsecutively for a current hysteresis time period using the currentcharacterization thresholds. The no occupant judgment includes either anempty seating area or nearly empty seating area. For example, an objectmay be left on a seat is judged as a nearly empty seating area. In thisexample, the thresholds may be set so that reset occurs for a change toan occupant or object similar in characteristics to a three year old orsmaller where the child category is based on a six year old or smaller.Other thresholds may be used. In one embodiment, the no occupantjudgment is repeated twice consecutively before resetting. Inalternative embodiments, once or three or more consecutive no occupantjudgments result in a reset. In yet other alternative embodiments, thenumber of judgments for reset based on no occupant is based on the timefor an occupant to leave the seat 22, seating area or automobile. Oncereset, the process returns to acts 34 or 36.

[0045] Additional sensor inputs may be used. For example, the seat beltsignal is input to the control processor 14. When the occupant sits andbuckles the seat belt, the occupant is not likely to change withoutunbuckling. Buckling may trigger initiation of the counter of act 38 ora change in characterization change parameters. Unbuckling may trigger areset or change in the characterization change parameters.

[0046] The air bag controller 16 suppresses deployment of the air bag 18where the output characterization is empty, associated with an object,or child. A object judgment is counted as a child judgment forcharacterizing the occupant. Deployment of the air bag 18 is enabledwhere the output characterization is adult.

[0047] In one embodiment, the characterization thresholds are the samefor distinguishing between an adult and a child. In other embodiments,overlapping thresholds are used to prioritize a type of classification.Thresholds are set to more easily change the classification from anadult to a child than from a child to an adult. For example, if theclassification is an adult, then the maximum load threshold forclassifying the occupant as a child is set higher than if theclassification began as a child. Likewise, the threshold for a car seatclassification may be different as a function of the most recent priorclassification, resulting in prioritizing between an adult and/or achild and a car seat. This prioritization provides a gray zone or areabetween the thresholds. For example, the lower threshold may be based onthe load for an average 6 year old child and the upper threshold may bebased on a 5th percentile adult female. Any occupant classified withinthe gray zone is classified according to the priority, such asclassification as a child. In this embodiment, the thresholds may bealtered to provide broader, narrower or no overlap as a function of timeor the confidence parameter.

[0048] While various embodiments have been described herein, changes andmodifications may be made without departing from the scope of theinvention which is defined by the following claims and equivalentsthereof.

What is claimed is:
 1. A vehicle passenger detection method forcontrolling sensing of an occupant in a seating area, the methodcomprising the acts of: (a) characterizing the occupant in the seatingarea as one of at least two categories; (b) applying a characterizationchange parameter for a first time period; and (c) altering thecharacterization change parameter after the first time period.
 2. Themethod of claim 1 wherein (b) comprises applying a hysteresis to (a) forthe first time period, and (c) comprises increasing an amount of time ofthe hysteresis.
 3. The method of claim 1 wherein (b) comprises applyinga characterization threshold and (c) comprises changing thecharacterization threshold so the one of the at least two categories ismore inclusive.
 4. The method of claim 1 further comprising: (d)determining a confidence parameter; wherein the first time period is afunction of the confidence parameter.
 5. The method of claim 4 wherein(d) comprises determining a ratio of occurrences of a first of the atleast two categories to a total number of judgments.
 6. The method ofclaim 1 further comprising: (d) altering a different characterizationchange parameter after a second time period, the second time perioddifferent than the first time period.
 7. The method of claim 2 furthercomprising (d) determining a ratio of occurrences of a first of the atleast two categories to a total number of judgments in a second timeperiod, the second time period longer than the first time period; and(e) if the ratio indicates a high confidence, altering acharacterization threshold parameter; and (f) if the ratio indicates alow confidence: (f1) waiting for a third time period; and (f2) alteringthe characterization threshold parameter if the characterization of (a)is consistent during the third time period.
 8. The method of claim 1further comprising: (d) determining first and second confidenceparameters at first and second times, the first time different than thesecond time, the first confidence parameter a function of a first totalnumber of judgments at the first time and the second confidenceparameter a function of second total number of judgments at the secondtime.
 9. The method of claim 1 further comprising: (d) resetting thecharacterization change parameter in response to no occupantcharacterization.
 10. The method of claim 1 further comprising: (d)resetting the characterization change parameter in response tocharacterizing the occupant as a different one of the at least twocategories consecutively for a current hysteresis time period.
 11. Themethod of claim 1 wherein (a) comprises characterizing with a capacitivesensing system.
 12. The method of claim 1 further comprising: (d)controlling an air bag system in response to the characterization of(a).
 13. A vehicle passenger detection system for controlling thesensing of an occupant in a seating area, the system comprising: anoccupant detection sensor adjacent the seating area; and a controlprocessor operatively connected with the occupant detection sensor, thecontrol processor operative to characterize the occupant in the seatingarea as one of at least two categories, apply a characterization changeparameter for a first time period, and alter the characterization changeparameter after the first time period.
 14. The system of claim 13wherein the characterization change parameter comprises a hysteresisparameter.
 15. The system of claim 13 wherein the characterizationchange parameter comprises a characterization threshold, the controlprocessor operable to alter the characterization threshold so the one ofthe at least two categories is more inclusive.
 16. The system of claim13 wherein the control processor is operable to determine a confidenceparameter, the first time period being a function of the confidenceparameter.
 17. The system of claim 13 wherein the control processor isoperable to alter a different characterization change parameter after asecond time period, the second time period different than the first timeperiod.
 18. The system of claim 13 wherein the control processor isoperable to reset the characterization change parameter in response toone of: (a) a no occupant characterization or (b) characterizing theoccupant as a different one of the at least two categories consecutivelyfor a current hysteresis time period.
 19. The system of claim 13 whereinthe occupant detection sensor comprises an electrode antenna.
 20. Thesystem of claim 13 further comprising an air bag controller connectedwith the control processor.
 21. A vehicle passenger detection method forcontrolling sensing of an occupant in a seating area, the methodcomprising the acts of: (a) characterizing the occupant in the seatingarea as one of at least two categories; (b) determining acharacterization change parameter as a function of a probability ofcharacterization accuracy; (c) limiting a change of the characterizationof (a) by the characterization change parameter.
 22. The method of claim22 wherein (b) comprises determining a ratio of occurrences of a firstof the at least two categories to a total number of judgments.
 23. Avehicle passenger detection method for controlling sensing of anoccupant in a seating area, the method comprising the acts of: (a)characterizing the occupant in the seating area as one of at least twocategories; (b) altering a characterization change parameter after afirst time period; and (c) resetting the characterization changeparameter in response to one of: (a) a no occupant characterization or(b) characterizing the occupant as a different one of the at least twocategories consecutively for a current hysteresis time period.